Resilient tantalum tubes and a process for making same



Patented Oct. 19, 1948 RESILIENT TAN TALUM TUBES AND A PROCESS FOR MAKING SAME Paul Alfred Weiss, Chicago, 111., assignor to the United States of America. as represented by the Secretary of War No Drawing. Application May 2, 1945, Serial No. 591,641

12 Claims.

This invention relates to resilient tantalum tubes and a process for making same, and it is particularly directed to resilient tantalum tubes suitable for sutureless joinder of severed nerve ends, I

In recent years tantalum has been employed in the medical field, particularly the surgical branch, for repairing damaged tissues and bones. Because of its malleability, tantalum can be drawn into very fine Wires, which are excellent for linking severed nerves, blood vessels, muscles,

tendons and skin. Likewise, tantalum foil has been fashioned into cylinders replacing conduits in the body, such as artery sections. Because of the ease with which tantalum foil may be fashioned into plates and the like, it has been used as panels to restore the natural contours of shattered skulls and as embedded plates in damaged abdomen walls. However, due to this extreme malleability of tantalum foil, it is unsuitable for the purpose of sutureless nerve splicing.

, Tantalum is particularly useful in the surgical field because it is completely inert and harmless in the human body. None of the body fluids or tissues corrode it; and, it does not irritate or damage any of the human tissues.

Elastic cuffs or sleeves formed from arteries hav previously been used for reuniting severed nerve stumps, but extreme difficulty has been encountered in obtaining this material in sufiicient quantities to meet the ever increasing demand in the surgical field. Because of the above-discussed properties of tantalum it was first thought that tantalum foil was the solution to this problem, but upon a closer investigation and experimentation it was found that other properties of tantalum, such as its pliability, rendered it unsuitable for this use.

A device for sutureless sleeve splicing of nerves, in addition to being inert and harmless in the human body, must be distensible, so as to permit 'it to be easily slidable onto the nerve stumps;

2 vide a process for making elastic tantalum tubes from malleable tantalum foil.

A further object of this invention is to provide a method for heat treating cylindrical rolls of tantalum foil to provide highly resilient tantalum tubes having increased structural strength.

The foregoing and other objects and advantages of this invention will be apparent from the following description.

This invention is based on the discovery that tantalum foil can be formed into cylinders of the desired dimension and of the desired resilience by gradient heat tempering. The procedure in volvesthree primary steps, comprising wrapping pliable tantalum foil around a heat conducting and radiation transmitting core; exposing the wrapped core to radiant heat and thereafter trimming overheated portions from the resultant cylinder.

The implements necessary in the procedure are a furnace adapted to provide an even heat and having heat control means; heat conducting and radian heat transmitting core tubing corresponding in size to the various nerve sizes, this tubing being preferably formed from quartz; heat conducting core rods, preferably steel, adapted to be fitted into the various tubes to complete the cores; and, fine steel wire for securing the foil to the core tubing.

Tantalum foil in varying degrees of thicknesses were tested, and those having a thickness Varying between 0.0004 and 0.00075 inch were found to be satisfactory, and those being approximately 0.0005 inch thick were found to be the best. This thickness makes sleeves of the proper strength and resilience, while sleeves made from foil more than 0.00075 inch thick were too strong and resilient and, unless fitted very accurately, tended to produce nerve compression, whereas sleeves made from foil less than 0.0004 inch thick required a degree of control in temperature too fine for practical purposes and, therefore, overheated, producing a brittl sleeve.

In the first step of the process, namely the wrapping, pliable tantalum foil, preferably 0.0005 inch thick, is cut into rectangular pieces. The short side should measure at least twice the circumference of the core to be used and preferably slightly more. For instance, for a spacer tube measuring 15 mm, in circumference one would allow a little more than 30 mm. width of foil. The

foil is then wrapped around the quartz tube or cylinder. The resulting rolls, therefore, consist of two turns, an inner turn and an over-lapping outer turn.

By tucking the edge in firmly and turning the quartz cylinder with friction against the foil, the foil wrapping can be made to fit over the quartz core tightly. It has been found desirable, if not essential, that there be no space left between the quartz core and the foil. Thin steel wire is wound around the foil in spiral turns to hold the foil tightly in position. The steel rod is then introdduced into the quartz tubing and the assembly is ready for the heat treatment.

The latter assembly is introduced into the interior of an electric furnace, which is set at approximately 800 (3., care being taken to avoid contact with the furnace walls. I-Ieatis thereby conveyed to the outer surface of the foil by radiation, and to the inner surface by conduction and 7 I ing between the inner and outer surface thermosets the foil in this predetermined cylindrical form andat the same time renders it resilient;

The correct degree of temperature and period of exposure in the furnace have to be determined empirically for each size of core assembly employed. Underexposure leaves the foil somewhat pliable, while overexposure makes it brittle and useless. To demonstrate the approximate temperature and time of exposure necessary for satisfactory treatment, a two inch sleeve over a mm. circumference quartz tube requires about one to one and one-half minutes exposure in a furnace at approximately 800 C. Upon removal from the furnace, the exposed surface of the sleeve should show a light opalescent tinge; heavier discoloration, such as brown or blue tones, indicates overheating. Obviously, higher degrees of temperature would require shorter period of exposure, and conversely. Due to the relatively short period of exposure necessary to impart the proper temper, the best results have been obtained by regulating the furnace at approximately 800 C.

After the proper temper has been obtained, the assembly is removed from the furnace and the sleeves stripped off the core.- Because of the tempering process more overlap is allowed in making the sleeve than is necessary in the surgical application, and, therefore, the edges should be trimmed. Trimming is best done by opening the sleeve'and flattening it under a glass plate, the ground edge of which serves as a cutting guide.

The gradient of elasticity from the outer to the inner edge causes the sleeve to assume different curvatures in the different parts. In general, the inner edge presses outwardly and thereby tends to increase the diameter of the sleeve, while the outer sleeve presses downwardly or inwardly thereby maintaining the cylindrical shape of the tube. If the size of the tube or sleeve turns out to be too small, some correction can be made by trimming the outer edge; on the other hand, if the inner edge tends to open the lumen too wide, an appropriate strip can be cut off the inner edge. In general, trimming the ends until the sleeve retains about one-half turn overlap produces the best results. Sometimes the end portions of the sleeves are overheated and these should be trimmed in order to prevent chipping due to the brittleness of these overheated portions.

Owing to its differential elasticity, each roll when opened and allowed to recoil by itself, forms a spiral scroll rather than a tube. In order to return such a reversely wound roll to its cylindrical shape, a pointed rod is inserted into the inner turn, the free edge tucked under the rod, and the outer end is then easily lapped over.

There are several methods for applying the resilient tantalum sleeves of this invention in sutureless junction of severed nerve ends. The most convenient method, however, i to employ two sleeves of different lengths having adjacent end sections adapted to overlap, in the fashion of stove pipe joinders. In placing the tantalum sleeves over the nerve ends, it is preferable to treat them as tubes and slip them over the nerve rather than to uncoil the sleeves and recoil them around the nerve. The sleeves may be slipped on the nerve by the splicing clutch method described in Proc. Soc. Exper. Biol. and Med, vol. 54, p. 275, 1943. Another suitable method is the suction canula method wherein the sleeve is pulled over a canula. The nerve end is sucked into the canula by means of syringe attached thereto, and the sleeve slipped off the canula onto the nerve when the canula releases the nerve. Lacking the equipment of either type described in the above processes, one may pull a tantalum wire through the epineurium of the cut surface, thread the nerve through the sleeve, thereafter remove the wire and trim the epineurium so as to preclude its intrusion into the gap.

The short sleeve is placed over the proximal stump and the long sleeve placed over the distal stump with the sleeve ends flush with the cut surface. The long sleeve is the actual link sleeve, and the shorter sleeve merely serves as an accessory to facilitate the linking. The two nerve stumps are brought close together, preferably within 5 mm. of each other; if necessary a long sling stitch through the nerve stumps at points remote from the cuts and beyond the sleeves; may be used to effect, this. The longer sleeve i then pulled down from the distal stump and telescoped over'the shorter sleeve encasi n'g the proximal stump, thereby positioning the nerve ends within the longer sleeve.

Past experiences indicate that the juncture between the nerve stumps is sufiiciently firm and organized within a few weeks to permit removal of the sleeve, if desired, without endangering the outcome. 1

This invention has been described in the manner that it would be utilized in the processes of sutureless joinder of severed nerves.

Having thus described my invention, what I claim as new and wish to secure by Letters Patent 1. In a process for preparing resilient tantalum tubes from tantalum foil, the steps of forming a cylinder comprising overlapping turns of pliable tantalum foil, and heat treating said cylinder in a manner such that a heat gradient exists between the inner surface and outer surface of said cylinder, with the inner surface of the cylinder being the cooler surface, and the outer surface being the hotter surface, the said tantalum foil cylinder being heated to a temperature and time sufficient to produce a permanent cylindrical deformation of the foil, whereby the foil permanently retains a cylindrical tubular configuration.

2. In a process for preparing resilient tantalum tubes from pliable tantalum foil, the steps comprising tightly wrapping pliable tantalum 'foil around a heat conduction and radiation transmitting cylinder having a heat conducting material inserted therein, andhea'ting said tantalum foil wrapped cylinder by radiation to a temperature and for a time suflicient to produce a permanent cylindrical configuration in the foil, wherebythe foil retains a tubular shape when removed from the cylinder. 7

3. In a process for preparing resilient tantalum tubes from pliable tantalum foil, the steps comprising tightly wrapping pliable tantalum foil around a quartz cylinder, inserting a steel core in said quartz cylinder, and heating said steel core and tantalum foil wrapped quartz tube by radiation of a temperature and time sufficient to produce a permanent cylindrical configuration in the foil and until the outer surface of said tantalum foil exhibits an opalescent tinge.

4. The process of claim 3 wherein the tantalum foil has a thickness of between 0.0004 and 0.00075 inch.

5. The process of claim 3 wherein the tantalum foil is approximately 0.0005 inch thick.

6. A resilient tantalum tube comprising overlapping longitudinal edges possessing a gradient of resiliency from the outer to the inner edge.

7. A sutureless joint adapted for use in joining severed nerve ends comprising a preformed tantalum cylinder having overlapping longitudinal edges and a gradient of elasticity from the outer longitudinal edge to the inner longitudinal edge.

8. A sutureless joint adapted for use in joining severed nerve ends comprising a preformed tantalum cyilnder having overlapping longitudinal edges and a gradient of elasticity from the outer longitudinal edge to the inner longitudinal edge, and said preformed tantalum cylinder having an inside diameter substantially the same as the diameter of the nerve to be joined.

9. A sutureless joint adapted for use in joining severed nerve ends comprising a, plurality of preformed telescoping tantalum cylinders, each said cylinder having overlapping tantalum longitudinal edges and a gradient of elasticity from the outer longitudinal edge to the inner longitudinal edge.

10. A sutureless joint adapted for use in joining severed nerve ends comprising a preformed tantalum cylinder having a, thickness between 0.0004 and 0.00075 inch, said cylinder having overlapping longitudinal edges and a gradient of elasticity from the outer longitudinal edge to the inner longitudinal edge.

11. A sutureless joint adapted for use in joining severed nerve ends comprising a preformed tantalum cylinder having a thickness approximately 0.0005 inch, said cylinder having overlapping longitudinal edges and a gradient of elasticity from the outer longitudinal edge to the inner longitudinal edge.

12. In a process for producing resilient tantalum tubes as defined in claim 1, the improvements which consist in heating the foil while in the cylindrical configuration by radiant heat radiating from a source thereof to a. temperature and for a time sufiicient to cause the foil to exhibit a light opalescent tinge during the heating thereby producing permanency in the cylindrical configuration and resiliency in the foil.

PAUL ALFRED WEISS;

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 397,861 Kelly Feb. 12, 1889 947,146 Bolton Jan. 18, 1910 1,470,707 Bates Oct. 16, 1923 2,015,509 Austin Sept. 24, 1935 2,127,903 Bowen Aug. 23, 1938 2,332,826 Fryer et al Oct. 26, 1943 OTHER REFERENCES Welding Encyclopedia, 10th ed., page 603, 1941. (On file in Division 3 of the Patent Office.) 

